cpg: add spread spectrum control

Disables spread spectrum by default so that the frequency estimations of
the CPG driver (notably used by the timer driver and libprof) are more
accurate.

TODO

@@ -3,17 +3,11 @@ For the 2.1.0 release:
 * project:   remove the compat branch
 * project:   remove the gray aliases
 
-Issues:
-* #10        support fx-CG 20
-
 Extensions on existing code:
 * tmu:       make interrupt handlers more elegant
 * bopti:     try to display fullscreen images with TLB access + DMA on fxcg50
-* topti:     support unicode fonts
 * dma:       fx9860g support (need to switch it on and update the Makefile)
 * core:      try to leave add-in without reset in case of panic
-* hardware:  fill in the HWMEM_FITTLB flag
-* cpg:       spread spectrum on fxcg50
 * core:      use cmp/str for memchr()
 * r61524:    brightness control and clean the file
 * core:      review forgotten globals and MPU addresses not in <gint/mpu/*.h>
@@ -21,6 +15,7 @@ Extensions on existing code:
 * core:      run destructors when a task-switch results in leaving the app
 * core:      invoke main menu instead of returning after main() ends
 * core rtc:  use qdiv10 to massively improve division performance
+* topti:     let the font specify letter and word spacing
 
 Future directions.
 * A complete file system abstraction

include/gint/mpu/cpg.h

@@ -65,8 +65,13 @@ typedef volatile struct
 		uint32_t CKOFF	:1;	/* CKO Output Stop */
 		uint32_t	:1;
 	);
-	/* TODO: CPG: Add the SSCGCR register */
-	pad(0x28);
+
+	pad(0x1c);
+	lword_union(SSCGCR,
+		uint32_t SSEN	:1;	/* Spread Spectrum Enable */
+		uint32_t	:31;
+	);
+	pad(0x8);
 
 	lword_union(FLLFRQ,
 		uint32_t	:16;

src/cpg/cpg.c

@@ -113,11 +113,17 @@ static void sh7305_probe(void)
 #undef CPG
 
 //---
-//	Other driver stuff
+//	Initialization, contexts and driver metadata
 //---
 
 static void init(void)
 {
+	/* Disable spread spectrum in SSGSCR */
+	if(isSH4())
+	{
+		SH7305_CPG.SSCGCR.SSEN = 0;
+	}
+
 	/* This avoids warnings about sh7705_probe() being undefined when
 	   building for fxcg50 */
 	#if defined(FX9860G) || (!defined(FX9860G) && !defined(FXCG50))
@@ -126,9 +132,31 @@ static void init(void)
 	sh7305_probe();
 }
 
+typedef struct {
+	uint32_t SSCGCR;
+} ctx_t;
+
+static ctx_t sys_ctx, gint_ctx;
+
+static void ctx_save(void *ctx)
+{
+	ctx_t *c = ctx;
+	if(isSH4()) c->SSCGCR = SH7305_CPG.SSCGCR.lword;
+}
+
+static void ctx_restore(void *ctx)
+{
+	ctx_t *c = ctx;
+	if(isSH4()) SH7305_CPG.SSCGCR.lword = c->SSCGCR;
+}
+
 gint_driver_t drv_cpg = {
-	.name    = "CPG",
-	.init    = init,
+	.name         = "CPG",
+	.init         = init,
+	.sys_ctx      = &sys_ctx,
+	.gint_ctx     = &gint_ctx,
+	.ctx_save     = ctx_save,
+	.ctx_restore  = ctx_restore,
 };
 
 GINT_DECLARE_DRIVER(1, drv_cpg);